Conventionally, to reduce the switching noise of a semiconductor integrate circuit device (hereinafter referred to as “IC chip”) and stabilize its operation power supply voltage, a capacitor is provided in a wiring board that is mounted with the IC chip. As for the manner of mounting the capacitor on the wiring board, as the lengths of interconnections between the IC chip and the capacitor increase, the inductance components of the interconnections increase and it becomes more difficult to attain the above effects sufficiently. It is therefore desirable that the capacitor be disposed as close to the IC chip as possible. JP-A-2005-39243 proposes a wiring board in which a core board located right under an IC chip accommodates a ceramic sub-core that incorporates a capacitor.